I play them for the game being fun. This means I have played through FF1 dozens of times, disregarding its paper thin plot and crap ending. I've played through FF3 more than once, and I like FF8 so much gameplay-wise that I'm usually not bothered with the insane amount of dialogue through which one must trudge. To me it's all about it having a fun battle and menu system to play around with. Games that ended up not appealing to me included FF12, which just got monotnous (Gambits? Please, their popularity is just a testament to how lazy gamers are getting. It's bad enough that when I have to go into the Games Development classroom the smell is unbearable.) and, initially, FF6 (though I've since gotten over it) for feeling like an endless supply of dungeon crawlers during the latter stages of the game.

As for "hardcore" playing? Hardcore's more of a music thing to me these days :/ Generally I like to play through a game a couple of times, then familiarise myself with it enough that the next time I can run through it I can defeat bosses in as few turns as possible by knowing exactly how they'll fight and what's gonna be available to me. That's ultimately what I play them for; the ability to feel smart overpowered and break the system somewhat. Obviously this is easiest in FF8 where you just exploit Limit Breaks :P This sometimes does mean a little bit of grinding, but usually I end up fetching every ridiculously overpowered means of defeating stuff as a matter of course by just learning the game, with minimal sidetracking time invested.